Inhibitory effect of exosomes secreted by human umbilical cord mesenchymal stem cells on apoptosis of oxygen-glucose deprived reoxygenation model of venous endothelial cells

Objective To explore the inhibitory effect of exosomes secreted by human umbilical cord mesenchymal stem cells(HUCMSC) on apoptosis of human umbilical vein endothelial cells(HUVEC) after model group(oxygen-glucose deprivation reoxygenation), and to clarify its possible mechanism. Methods Human umbilical cord mesenchymal stem cells were cultured. The collected cell supernatant was stored in a centrifugal tube. The exosomes secreted by human umbilical cord mesenchymal stem cells were extracted by ultracentrifugation and identified. Human umbilical vein endothelial cells were randomly divided into control group, model group and different concentrations of HUCMSC-EXO(20 μg/ml, 40 μg/ml, 60 μg/ml) treatment groups(adding HUCMSC-EXO into the model group) . The morphological changes of HUVEC cells in each group were observed by inverted phase contrast microscope, and the proliferation inhibition rate of HUVEC in each group was measured by CCK-8 reagent. Western blot was used to detect the expression of apoptosis-related proteins Caspase-3, Bax, Bcl-2 and hypoxia-associated protein hypoxia inducible factor 1α(HIF-1α). Inhibitor(HIF-1α inhibitor) + model group and HUCMSC-EXO + inhibitor + model group were added on the basis of the above experiments. Western blot analysis was performed to observe the effects of HUCMSC-EXO, inhibitor and both of them on HIF-1α and Bax expressions in HUVEC. Results HUCMSC-EXO was successfully extracted and identified. Compared with the control group, the volume of HUVEC in the model group and the HUCMSC-EXO group with different concentrations decreased, became round, connected and evacuated, and the growth state was poor under the inverted phase contrast microscope.CCK-8 detection showed that the cell viability in the HUCMSC-EXO group was significantly higher than that in the model group, the difference was statistically significant (t=9.23, P 0.05)and Bax protein ((0.363±0.069), (0.370±0.064); t=0.18, P>0.05). But both of them were down-regulated compared with the model group (HIF-1α protein (0.919±0.064), Bax protein (0.902±0.071)), the differences were significant( t=13.56, t=13.03, both P<0.05). Conclusion HUCMSC-EXO has a protective effect on OGD/R model of HUVEC, and its mechanism may be related to the down-regulation of HIF-1α expression. Key words: Human umbilical mesenchymal stem cells; Exosomes; Oxygen-glucose deprivation reoxygenation; Human umbilical venous endothelial cells; Apoptosis